Prepare the Teriyaki Sauce:
In a medium saucepan, combine the soy sauce, 1/4 cup water, honey (or brown sugar), rice vinegar, minced garlic, and grated ginger. Heat over medium heat, stirring occasionally, until the mixture begins to simmer.
In a small bowl, mix the cornstarch with 1 tablespoon of water to create a slurry. Slowly add the slurry to the simmering sauce, whisking continuously until the sauce thickens. Remove from heat and set aside.
Cook the Chicken:
Season the chicken pieces with salt and pepper.
Heat the vegetable oil in a large skillet or wok over medium-high heat. Add the chicken and cook until browned and cooked through, about 5-7 minutes.
Combine Chicken and Sauce:
Pour the prepared teriyaki sauce over the cooked chicken in the skillet. Stir well to coat the chicken evenly with the sauce. Cook for another 2-3 minutes, allowing the chicken to absorb the flavors.
Serve:
Serve the teriyaki chicken over a bed of cooked white rice. Garnish with sliced green onions and sesame seeds if desired.